ARRL Propagation Bulletin ARLP024 (2003)

SB PROP @ ARL $ARLP024
ARLP024 Propagation de K7RA
ZCZC AP24
QST de W1AW
Propagation Forecast Bulletin 24 ARLP024
From Tad Cook, K7RA
Seattle, WA June 13, 2003
To all radio amateurs
SB PROP ARL ARLP024
ARLP024 Propagation de K7RA
Geomagnetic disturbances continued this week, but at a lower level
than the previous seven days (our reporting week runs from Thursday
through the following Wednesday). The average daily planetary A
index for the week dropped to 21 from 37.1 the previous week. The
average daily sunspot number rose from 67.4 to 149.4, reaching a
peak of 207 on Tuesday, June 10. Solar flux increased as well, the
weekly average rising from 117.4 to 150.5. Solar flux peaked at
192.9 on Wednesday, June 11. Solar flux over the weekend is expected
to be 150, 140, 130 and 120 for Friday through Monday.
With all of the recent geomagnetic disturbances, there is hope for
HF operators with the predicted planetary A index of 12 for June 13
and June 16. This is only slightly unsettled, much better than the A
index of 20 to 30 we've seen recently. However, be aware that flares
can pop up and conditions can change, as it did recently on May 30,
which was forecast for so long to have quiet conditions. Now it
seems there was a coronal mass ejection that could hit earth on June
13, causing a rise in geomagnetic indices.
A couple of large sunspots were news this week, causing the rise in
sunspot numbers and some flares as well. A good view is Tuesday's
solar disk, seen at
http://science.nasa.gov/spaceweather/images2003/10jun03/midi512_blank.gif.
Notice the "10jun03" characters in that URL. You can change those to
11jun03, then 12jun03 and 13jun03, then click "back" with your
browser to display as a simple animation.
Check out Project Jove at http://radiojove.gsfc.nasa.gov/. Dick
Flagg, AH6NM and Jim Sky, KH6SKY built a spectrograph that scans
18-28 MHz, recording radio noise from the Sun and Jupiter. They are
about to release software that lets anyone view spectrograms in real
time from data streamed via the internet. Recently they observed a
solar burst during flare activity, and just prior to the burst you
can see HF signals present between 18-28 MHz. Right after the burst
is nothing, due to a radio blackout. The images were on
http://www.spaceweather.com yesterday, and unfortunately are now
gone. Perhaps by next week we can come up with a link to the images.
Bob Sluder, N0IS says he has a very simple 6 and 2-meter setup with
only a 2-meter loop and a 6-meter Halo in his attic. But on
Thursday, May 5 he heard stations from around North America on
2-meters and on 6-meters the North and South America openings lasted
24 hours. Bob writes, "So, bring on another BIG BLAST from the sun
and lets see what happens. Hooray for high K's. Too bad about those
high A numbers, but then, if you are on VHF, you would not care."
Going a little further back into May, Bill Cullen, WH6DQ who lives
3,500 feet up the side of Kilauea on Hawaii's Big Island reports
that on May 23 around 0100z he heard the 147.09 MHz repeater on
Catalina Island in California. He listened to a couple of California
stations converse, broke in, but wasn't copied, even though he could
trigger the repeater. He observes that the two California hams would
have been excited if they only knew where he was. So, if you were on
147.09 MHz in Southern California around 0100z on May 23 and heard a
not quite copy able station break in, it was Bill.
Rodney Vorndam, K9ROD wrote to say that last Saturday, June 7 was a
great day for him on 6-meters in Colorado. He made 25 contacts
across the south and central parts of the U.S., and one on 6-meters,
while running just 10-watts. He's noticed great 6-meter conditions
coinciding with large storm centers moving across the U.S. in the
summer.
Dan Jeswald, W4NTI also commented on large storm fronts, saying he
has good luck during the summer E-skip season aiming his 3-element
homebrew 6-meter Yagi at storms. On the same day K9ROD in Colorado
was having so much fun, W4NIT in Anniston Alabama was hearing
France, Italy and Portugal at S5-S7 on 6-meters. K9ROD wrote again
to say that Tuesday, June 10 was his best night on 6-meters ever.
The band was full and he made 26 contacts across the U.S.
The day prior, Monday June 9, Al Olcott, K7ICW in Nevada reported an
all day 6-meter opening that suddenly intensified. He noticed a lot
of QRM on broadcast television frequencies, and at 2319z he heard
W5HOT in Arkansas at S9. On 2-meters shortly after this he noticed
pandemonium. He made 11 W5 contacts in Arkansas, Louisiana, Texas
and Oklahoma. He tried 222 MHz, but got no response. He believes
there was a highly reflective ionospheric cloud in the E-layer
centered over DM83 on the Texas-New Mexico border.
Carl Luetzelschwab, K9LA had some interesting insight regarding
trans-equatorial propagation during high geomagnetic activity,
mentioned in last week's bulletin. He writes, "There's been much
study in the area of how geomagnetic storms affect the ionosphere.
One piece of knowledge to come out of this is that all geomagnetic
storms are not equal, and thus the effect on the ionosphere can
vary."
He continues, "For gradually evolving storms, driven by slowly
increasing southward IMF, the low to mid-latitude ionosphere tends
toward an increase in ionization at night - sometimes up to a 50%
increase in foF2. So there really is an ionospheric basis for
enhanced north-south propagation. On the other hand, storms with an
initial compressive phase and rapidly evolving main phase tend to
deplete nighttime mid-latitude ionization." Thank you, Carl!
For more information on propagation and an explanation of the
numbers used in this bulletin see the Propagation page on the ARRL
Web site at http://www.arrl.org/tis/info/propagation.html. You can
write to the author of this bulletin at k7ra@arrl.net.
Sunspot numbers for June 5 through 11 were 95, 98, 125, 167, 176,
207, and 178, with a mean of 149.4. 10.7 cm flux was 113.6, 125.6,
133.2, 153.4, 158.3, 176.5, and 192.9, with a mean of 150.5.
Estimated planetary A indices were 13, 13, 24, 27, 28, 27, and 15,
with a mean of 21.
NNNN
/EX